.\" LIC: GPL
.TH PPPOE-RELAY 8 "26 January 2001"
.\""
.UC 4
.SH NAME
pppoe-relay \- user-space PPPoE relay agent.
.SH SYNOPSIS
.B pppoe-relay \fR[\fIoptions\fR]

.SH DESCRIPTION
\fBpppoe-relay\fR is a user-space relay agent for PPPoE
(Point-to-Point Protocol over Ethernet) for Linux.  \fBpppoe-relay\fR
works in concert with the \fBpppoe\fR client and \fBpppoe-server\fR
server.  See the OPERATION section later in this manual for
details on how \fBpppoe-relay\fR works.

.SH OPTIONS
.TP
.B \-S \fIinterface\fR
Adds the Ethernet interface \fIinterface\fR to the list of interfaces
managed by \fBpppoe-relay\fR.  Only PPPoE servers may be connected to
this interface.

.TP
.B \-C \fIinterface\fR
Adds the Ethernet interface \fIinterface\fR to the list of interfaces
managed by \fBpppoe-relay\fR.  Only PPPoE clients may be connected to
this interface.

.TP
.B \-B \fIinterface\fR
Adds the Ethernet interface \fIinterface\fR to the list of interfaces
managed by \fBpppoe-relay\fR.  Both PPPoE clients and servers may be
connected to this interface.

.TP
.B \-n \fInum\fR
Allows at most \fInum\fR concurrent PPPoE sessions.  If not specified,
the default is 5000.  \fInum\fR can range from 1 to 65534.

.TP
.B \-i \fItimeout\fR
Specifies the session idle timeout.  If both peers in a session are idle
for more than \fItimeout\fR seconds, the session is terminated.
If \fItimeout\fR is specified as zero, sessions will never be terminated
because of idleness.

Note that the idle-session expiry routine is never run more frequently than
every 30 seconds, so the timeout is approximate.  The default value for
\fItimeout\fR is 600 seconds (10 minutes.)

.TP
.B \-F
The \fB\-F\fR option causes \fBpppoe-relay\fR \fInot\fR to fork into the
background; instead, it remains in the foreground.

.TP
.B \-h
The \fB\-h\fR option prints a brief usage message and exits.

.SH OPERATION

\fBpppoe-relay\fR listens for incoming PPPoE PADI frames on all interfaces
specified with \fB-B\fR or \fB-C\fR options.  When a PADI frame appears,
\fBpppoe-relay\fR adds a Relay-Session-ID tag and broadcasts the PADI
on all interfaces specified with \fB-B\fR or \fB-S\fR options (except the
interface on which the frame arrived.)

Any PADO frames received are relayed back to the client which sent the
PADI (assuming they contain valid Relay-Session-ID tags.)  Likewise,
PADR frames from clients are relayed back to the matching access
concentrator.

When a PADS frame is received, \fBpppoe-relay\fR enters the two peers'
MAC addresses and session-ID's into a hash table.  (The session-ID seen
by the access concentrator may be different from that seen by the client;
\fBpppoe-relay\fR must renumber sessions to avoid the possibility of duplicate
session-ID's.)  Whenever either peer sends a session frame, \fBpppoe-relay\fR
looks up the session entry in the hash table and relays the frame to
the correct peer.

When a PADT frame is received, \fBpppoe-relay\fR relays it to the peer
and deletes the session entry from its hash table.

If a client and server crash (or frames are lost), PADT frames may never
be sent, and \fBpppoe-relay\fR's hash table can fill up with stale sessions.
Therefore, a session-cleaning routine runs periodically, and removes old
sessions from the hash table.  A session is considered "old" if no traffic
has been seen within \fItimeout\fR seconds.  When a session is deleted because
of a timeout, a PADT frame is sent to each peer to make certain that they
are aware the session has been killed.

.SH EXAMPLE INVOCATIONS

.nf
pppoe-relay -C eth0 -S eth1
.fi

The example above relays frames between PPPoE clients on the eth0 network
and PPPoE servers on the eth1 network.

.nf
pppoe-relay -B eth0 -B eth1
.fi

This example is a transparent relay -- frames are relayed between any mix
of clients and servers on the eth0 and eth1 networks.

.nf
pppoe-relay -S eth0 -C eth1 -C eth2 -C eth3
.fi

This example relays frames between servers on the eth0 network and
clients on the eth1, eth2 and eth3 networks.

.SH AUTHORS
\fBpppoe-relay\fR was written by Dianne Skoll <dfs@roaringpenguin.com>.

The \fBpppoe\fR home page is \fIhttp://www.roaringpenguin.com/pppoe/\fR.

.SH SEE ALSO
pppoe-start(8), pppoe-stop(8), pppoe-connect(8), pppd(8), pppoe.conf(5),
pppoe(8), pppoe-setup(8), pppoe-status(8), pppoe-sniff(8), pppoe-server(8)

